#gallery {
    column-count: 4;
    column-gap: 20px;
}

#gallery img {
    width: 100%;
    height: auto;
    margin: 4% auto;
    box-shadow: -3px 5px 15px #000;
    cursor: pointer;
    transition: all 0.2s;
}

@media (max-width:1200px){
    #gallery{
    column-count:4;
    column-gap:20px;
  }
}
@media (max-width:800px){
    #gallery{
    column-count:3;
    column-gap:20px;
  }
}
@media (max-width:600px){
    #gallery{
    column-count:2;
  }
}